Fungal diversity differences in the indoor dust microbiome from built environments on earth and in space

Human occupied built environments are no longer confined to Earth. In fact, there have been humans living and working in low-Earth orbit on the International Space Station (ISS) since November 2000. With NASA’s Artemis missions and the age of commercial space stations set to begin, more human-occupied spacecraft than ever will be in Earth’s orbit and beyond. On Earth and in the ISS, microbes, especially fungi, can be found in dust and grow when unexpected, elevated moisture conditions occur. However, we do not yet know how indoor microbiomes in Earth-based homes and in the ISS differ due to their unique set of environmental conditions. Here we show that bacterial and fungal communities are different in dust collected from vacuum bags on Earth and the ISS, with Earth-based homes being more diverse (465 fungal OTUs and 237 bacterial ASVs) compared to the ISS (102 fungal OTUs and 102 bacterial ASVs). When dust from these locations were exposed to varying equilibrium relative humidity conditions (ERH), there were also significant fungal community composition changes as ERH and time elevated increased (Bray Curtis: R2 = 0.35, P = 0.001). These findings can inform future spacecraft design to promote healthy indoor microbiomes that support crew health, spacecraft integrity, and planetary protection.


Figure S2 :
Figure S2: Fungal Richness and Shannon diversity plots for 6-hour time of wetness samples comparing relative humidity (RH) conditions (85% and 100% RH) for Earth-based house dust and dust collected from the ISS.Location is indicated by color (Earth -Red, ISS-Blue).** Indicates Kruskal-Wallis t-test significance of P < 0.001, while *** indicates P < 0.0001.

Figure S3 :
Figure S3: Fungal Richness and Shannon diversity plots for 12-hour time of wetness samples comparing relative humidity (RH) conditions (85% and 100% RH) for Earth-based house dust and dust collected from the ISS.Location is indicated by color (Earth -Red, ISS-Blue).** Indicates Kruskal-Wallis t-test significance of P < 0.001, while *** indicates P < 0.0001.

Figure S4 :
Figure S4: Fungal Richness and Shannon diversity plots for 18-hour time of wetness samples comparing relative humidity (RH) conditions (85% and 100% RH) for Earth-based house dust and dust collected from the ISS.Location is indicated by color (Earth -Red, ISS-Blue).** Indicates Kruskal-Wallis t-test significance of P < 0.001, while *** indicates P < 0.0001.

Figure S5 :
Figure S5: Fungal Richness and Shannon diversity plots for 24-hour time of wetness samples comparing relative humidity (RH) conditions (85% and 100% RH) for Earth-based house dust and dust collected from the ISS.Location is indicated by color (Earth -Red, ISS-Blue).*** Indicates Kruskal-Wallis t-test significance of P < 0.0001.

Figure S6 :
Figure S6: Bacterial beta diversity with Bray Curtis dissimilarity principal coordinate analyses plots for original dust samples.Location of dust samples are indicated by shape (Earthcircle, ISStriangle).Ellipses represent 95% confidence interval for each set of data.

Figure S7 :
Figure S7: Bacterial Richness and Shannon diversity plots for original dust samples comparing Earth-based house dust to dust collected from the ISS.* Indicates Kruskal-Wallis t-test significance of P < 0.05.

Table S1 :
Adonis values for fungal beta diversity based on Bray-Curtis Dissimilarity between Earth-based residential house dust and dust collected from the International Space Station.

Table S2 :
Fungal and bacterial alpha diversity comparisons between Earth-based and ISS dust for all conditions compared in this study.
Figure S1: Fungal beta Bray Curtis dissimilarity principal coordinate analyses plots for time of wetness (TOW) samples separated out by each TOW value.For each plot, location of dust samples was indicated

Table S4 :
Kruskal-Wallis test statistics for fungal alpha diversity metrics comparing Earth-based residential house dust to dust collected from the ISS.

Table S5 :
Differential abundance comparison of fungal species between Earth-based house dust and ISS dust in all TOW conditions (6, 12, 18, and 24 hours) at 100% RH.A total of 521 fungal species were identified where 26 were significantly more abundant in ISS samples and 456 were more abundant in Earth-based house dust.

Table S6 :
Kruskal-Wallis test statistics for bacterial alpha diversity metrics comparing Earth-based residential house dust to dust collected from the ISS.

Table S7 :
Adonis values for bacterial beta diversity based on Bray-Curtis Dissimilarity between Earth-based residential house dust and dust collected from the International Space Station

Table S8 :
Differential abundance comparison of bacterial species between Earth-based house dust and ISS dust in original dust samples.A total of 81 bacterial species were identified where 3 were significantly more abundant in ISS samples and 11 were more abundant in Earth-based house dust.